Two imidazole-functionalized ionic liquids as novel corrosion inhibitors for mild steel useful for industrial pickling process: An experimental and theoretical study

• S.Y. Cao^1,2, Y.B. Cao^1,2, Y. Zhao³, Y.W. Li⁴ and H. Wang^1,2

¹ School of Mechanical and Automation, WeiFang University, Weifang, 261061, China
² Shandong Key Laboratory of Intelligent Manufacturing Technology for Advanced Power Equipment, WeiFang University, Weifang, 261061, China
³ Corrosion and Protection Center, Northeastern University, Shenyang 110819, China
⁴ School of Chemical Engineering and Environment, WeiFang University of Science and Technology, Weifang, 262700, China

Abstract: Material degradation remains a persistent challenge in industrial applications, necessitating innovative corrosion control strategies to balance efficacy and environmental sustainability. However, the use of toxic inhibitors complicates corrosion control, highlighting the need for sustainable alternatives and a more comprehensive understanding of structure–inhibition relationship. This study systematically investigates alkyl imidazolium ionic liquids (ILs), including unmodified and functionalized variants with sulfonic acid (IL1) and amino (IL2) groups, as green corrosion inhibitors for mild steel in 1 M H₂SO₄ through integrated experimental and theoretical approaches. Electrochemical impedance spectroscopy (EIS) and polarization tests revealed that the inhibition efficiency followed the order: IL1＞IL2. The efficiency of IL1 increased with concentration, and its adsorption onto the steel surface conformed to the Langmuir isotherm, involving both physisorption and chemisorption. Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) analysis of the corroded steel surface confirmed the critical role of functional groups in governing inhibition performance. X-ray photoelectron spectroscopy (XPS) reveals chemical interactions between IL1/IL2 and Fe atoms, forming stable film for corrosion resistance. The theoretical results of quantum chemical study and molecular dynamics simulations are in good agreement with the experimental data, which confirms the proposed inhibition mechanisms on microscopic scale. This study contributed valuable perspectives to the design of efficient and eco-friendly multifunctional ILs inhibitors.

Keywords: corrosion inhibition, adsorption, multifunctional ionic liquids, carbon steel, theoretical calculations

Int. J. Corros. Scale Inhib., 2025, 14, no. 2, 930-961
doi: 10.17675/2305-6894-2025-14-2-26

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